Gemini Gems, Morning Jupiter Sports Spots, the Moon Slides Over a Star and Meets Prominent Planets, Mars Sees the Seven Sisters!

Star Walk
6 min readMar 25, 2019


(This image of the Eskimo Nebula in central Gemini was taken by Adam Block in 2015 using a very large telescope at the Mount Lemmon SkyCenter near Tucson, Arizona. His website of astro images is here.)

The Moon and Planets

Following last week’s full moon, the moon will spend this week waning and rising later while it swings toward next week’s meet-up with the sun (new moon). At this time of the moon’s monthly cycle, it will be rising after midnight and lingering into the morning daytime sky.

If you happen to be up for it, early on Monday morning, the moon will pass in front of (or occult) a fairly bright double star designated Theta Librae in Libra (the Scales). The leading edge of the moon will cover the star(s) at 12:30 am EDT (give or take, depending on your latitude on Earth) and the star(s) will pop out from behind the moon’s dark edge at 1:35 am. For observers in the GTA and surrounding region, the moon will be very low in the southeastern sky when the event begins, and somewhat higher at the end. Binoculars and small telescopes will both work for the occultation.

On Tuesday morning, in the southeastern pre-dawn sky, the moon will land above and between bright Jupiter (on the left) and the bright, reddish star Antares (on the right) in Scorpius (the Scorpion). On Wednesday morning, the waning gibbous moon will be positioned less than four finger widths to the lower left (east) of Jupiter. The duo will nicely fit within the field of view of binoculars. They’ll rise after 2:15 am local time and remain observable until mid-morning, allowing Jupiter to be found in daylight with binoculars, using the moon as a reference.

(Close approach of the Moon and Jupiter. The Moon will be 21 days old.)

Just after midnight on Wednesday, the moon will reach its last quarter phase, when it will appear half illuminated. On Friday morning, the waning crescent moon will be positioned less than three finger widths to the lower left (southeast) of Saturn. Hours earlier, observers in the eastern edge of Brazil, southern Africa, Madagascar, the southern tip of India, and Sri Lanka can see the moon occult Saturn. The moon will end this week as a gorgeous crescent shining over the eastern horizon before sunrise on both weekend mornings.

Mars will continue to be an easy planet to see every evening this week, but only for a couple of hours after dusk. By midnight, Mars will set in the west. Once the sky has darkened, look for Mars’ medium-bright, reddish pinpoint of light less than halfway up the western sky. Mars has been slowly shrinking in size and brightness as we increase our distance from it little-by-little. Distant Uranus is situated two fist diameters below Mars, in Pisces (the Fishes) — but it’s too low for observing nowadays.

In the western evening sky on Saturday, Mars’ eastward orbital motion will carry it within three finger widths of the bright open star cluster known as the Pleiades, the Seven Sisters, and Messier 45. For best results, view the pairing in binoculars while they are higher in the sky — before about 10 pm local time.

(This week, reddish Mars will occupy the western early evening sky for a few hours after dusk. Over the next two weeks, Mars’ eastward motion will carry it past the beautiful Pleiades Cluster in Taurus.)

As I inferred above, the eastern pre-dawn sky will host the moon and bright planets party this week. Bright Jupiter will rise first, at about 2 am local time. By 6:30 am, it should still be visible well above the southern horizon. Yellowish Saturn, will rise at about 4 am local time but, being dimmer than Jupiter, it will become lost in the southeastern twilight before 6:30 am. Look for Venus as a very bright beacon sitting very low over the east-southeastern horizon from 6 am local time until sunrise. In a telescope, Venus will exhibit a gibbous (more than half-illuminated) phase.

From time to time, the small round black shadows cast by Jupiter’s four Galilean moons become visible in amateur telescopes as they cross (or transit) the planet’s disk. On Monday, March 25, observers in North America can see two of those shadows on Jupiter at the same time. At 4:05 am EDT, Europa’s shadow will join Ganymede’s shadow already in transit near Jupiter’s northern pole. (Your telescope will invert and/or flip the image. Note how it affects the moon and apply that to everything else you look at with it.) The duo of black spots will cross Jupiter together for almost two hours until Ganymede’s shadow moves off the planet at 6:04 am EDT. Europa’s shadow will continue to transit for about another 30 minutes. More of these special events will occur, at more convenient times, in the coming months.

(Jupiter and its moons.)

Some Gemini Gems

In mid-evening during late March, the zodiac constellation of Gemini (the Twins) is high in the southwestern sky, above Orion. The constellation is dominated by the bright stars Castor and Pollux, which mark the twins’ heads. At first glance, those two stars look alike — but they actually have different brightnesses and colours. Castor is a white, magnitude 1.56 star of spectral class A1. A medium-sized telescope will resolve it into a fine double star with a separation of 5.2 arc-seconds — but the system is actually composed of six stars located 51 light-years from our sun! Castor is always on the right-hand side of the constellation when the twins are standing upright.

Pollux, the head of the more southerly (left-hand) twin, is slightly brighter at magnitude 1.17, and may once have been brighter than Castor. Pollux is a cool, yellow giant star located 34 light-years from the sun. Pollux is known to be orbited by a large, hot Jupiter exoplanet that has been assigned the name Thestias.

Both of the twins of Gemini dip their toes into the Milky Way, so the constellation includes many deep sky gems to look at. The lower right (southwestern) portion of Gemini hosts Messier 35, a beautiful, bright open star cluster composed of more than 100 brighter members. Some star maps label it the Shoe-Buckle Cluster. A fainter and more distant cluster designated NGC 2158 sits only a pinky finger’s width below (southwest of) Messier 35.

The Eskimo Nebula (also designated NGC 2420) is a spectacular planetary nebula visible in backyard telescopes. But use high magnification — it’s tiny! It actually resembles a head surrounded by a fur-lined parka. The magnitude 9.1 object sits a little more than 2 finger widths to the left (southeast) of the medium-bright star Wasat (Delta Geminorum), which marks Pollux’ waist. Another lovely open star cluster designated NGC 2420, and sometimes called the Twinkling Comet Cluster, is a bit higher than the Eskimo. Look for it sitting 4 finger widths to the upper left (east) of Wasat.

Astronomy Skylights for the week of March 24th, 2019 by Chris Vaughan.

Keep looking up, and enjoy the sky when you do. I love questions and requests — so, send me some!



Star Walk

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